Method and device for generating deformation twinning in a metal

ABSTRACT

A method of generating twin lamellas in a metal body includes the steps of introducing the metal body into a chamber, filling the chamber with a cooling medium having a temperature that will enable generation of twin lamellas in the metal body upon deformation thereof, and deforming the metal body while the latter is surrounded by the cooling medium. The cooling medium surrounds the metal body upon deformation of the latter is in a gaseous state. The present disclosure also relates to a device for generating twin lamellas in the metal body, the device including a chamber, a chamber inlet connected to a cooling medium source, and a deformation device arranged to deform the metal body. The deformation device is positioned inside the chamber so that the metal body will be surrounded by the cooling medium in a gaseous state while being deformed by the deformation device.

TECHNICAL FIELD

The present invention relates to a method of generating twin lamellas in a metal body, comprising the steps of introducing said metal body into a chamber, filling said chamber with a cooling medium having a temperature that will enable generation of twin lamellas in the metal body upon deformation thereof, and deforming said metal body while the latter is surrounded by said cooling medium.

The present invention also relates to a device for generating twin lamellas in a metal body, said device comprising a chamber, a chamber inlet connected to a cooling medium source, and a deformation device for deforming said metal body, said deformation device being positioned inside said chamber.

BACKGROUND

Deformation of metal, in particular wire drawing, in cryogenic media has been suggested by prior art for the purpose of enabling the formation of so called twin lamellas in the metal that is deformed. Twin lamellas are formed through a phenomenon known as “nano-twinning,” in which, during deformation, the atomic arrangements in adjacent crystalline regions of a material, such as a metal, form mirror images of one another. These nano-twins, or twin lamellas, are formed when the material undergoes plastic deformation at cryogenic temperatures. Liquid nitrogen has been suggested as a suitable cooling means. Thereby, metal wire which is subjected to a drawing operation in a die, in which the diameter of the metal wire is reduced, is positioned in liquid nitrogen, having a temperature of approximately −196° C. At such temperature, generation of twin lamellas in the metal wire is assumed to take place upon deformation thereof.

However, a drawback of prior art is that the efficiency of liquid nitrogen as a quench coolant is limited, as it will immediately boil when in contact with a warmer object (nitrogen boils at −195.8° C. at atmospheric pressure), thus enclosing the object in an insulating nitrogen gas. Another drawback is that there is a lack of possibility of adjusting the cooling temperature depending on the deformation conditions and the material to be deformed.

It is therefore an aspect of the present invention to suggest an alternative method and device for generating twin lamellas in a metal body which method provides improvement of the possibility of adjusting the cooling temperature applied to the metal body being deformed.

SUMMARY

The aspect of the present disclosure is obtained by means of a method of generating twin lamellas in a metal body, comprising the steps of

-   -   introducing said metal body into a chamber;     -   filling said chamber with a cooling medium having a temperature         that will enable generation of twin lamellas in the metal body         upon deformation thereof; and     -   deforming said metal body while the latter is surrounded by said         cooling medium;         wherein the cooling medium surrounding said metal body upon         deformation of the latter is in a gaseous state.

Cooling of the metal body by means of a cooling medium in a gaseous state will improve the possibility of adjusting the temperature of the cooling medium and, thereby, the metal body which is being deformed. The cooling of the metal body may be performed by using a cold gaseous medium, a gas mixed with liquid cooling medium, a direct metal to metal coolant system, or a combination thereof.

According to one embodiment of the method as defined hereinabove or hereinafter, the temperature inside said chamber is controlled by means of controlled introduction of said cooling medium into the chamber. In other words, control of the temperature in the chamber, and thereby of the metal body being deformed therein, is performed through an active and purposive control of the flow of cooling medium into the chamber.

According to one embodiment, the temperature inside the chamber is controlled by means of controlled introduction of said cooling medium into the chamber on at least two different locations within the chamber, wherein the cooling medium is on a first location directed directly onto the metal body being deformed, and on a second location directed onto a deformation device used to deform said metal body. Efficient cooling is thereby achieved, since cooling medium is on one hand used to directly cool the metal body, and on the other hand used to cool the deformation device such that indirect cooling of the metal body can be achieved.

According to one embodiment, the cooling medium has a temperature in the range of about −80° C. to about −195° C. In other words, the cooling medium surrounding said metal body during deformation of the latter has a temperature in the range of about −80° C. to about −195° C. According to another embodiment, the cooling medium has a temperature in the range of about −150° C. to about −195° C.

According to one embodiment, said cooling medium consists essentially of nitrogen. According to one embodiment, essentially is referred to as at least 50 atomic %. According to yet other embodiments, essentially is referred to as at least 60 atomic %, such as to at least 70 atomic %, such as to at least 80 atomic %, such as to at least 80 atomic %, such as to at least 90 atomic %.

According to one embodiment of the method as defined hereinabove or hereinafter, said cooling medium may be introduced in a liquid state into the chamber and is then, as result of the temperature and pressure reigning in the chamber, permitted to change to a gaseous state once introduced into said chamber. Also, the introduction technique affects the transition into gaseous phase. According to one embodiment, the cooling medium is sprayed into the chamber through nozzles. Thus, the cooling medium may be stored in liquid state, but may have its effect on said metal body in a gaseous state. Introducing the cooling medium into the chamber in a liquid state, as compared to introducing it in a gaseous state, also has the advantage of resulting in a better cooling efficiency.

According to one embodiment, said metal body is an elongated body which is continuously introduced into said chamber through an opening in the latter, and part of the cooling medium in a gaseous state may be removed from the chamber and used for pre-cooling of parts of said metal body that have yet not been introduced into the chamber. Pre-cooling of the said metal body contributes to a more precise temperature control thereof and improved cooling efficiency.

According to one embodiment, said metal body is a wire or tube and said deformation thereof inside said chamber includes a reduction of the thickness thereof.

The above mentioned aspect of the present disclosure is also achieved by means of a device for generating twin lamellas in a metal body, said device comprising

-   -   a chamber;     -   a chamber inlet connected to a cooling medium source; and     -   a deformation device for deforming said metal body, said         deformation device being positioned inside said chamber; wherein         the deformation device is positioned so that the metal body will         be surrounded by said cooling medium in a gaseous state while         being deformed by said deformation device.

According to on embodiment, said device comprises temperature control means for controlling the temperature inside said chamber by controlling the introduction of cooling medium into the chamber. Such temperature control means for controlling the temperature inside said chamber may include a control valve or similar equipment arranged in a conduit connecting the cooling medium source with said chamber inlet.

According to one embodiment, said temperature control means comprises at least a first and a second independently controllable nozzle positioned inside the chamber and configured to introduce cooling medium into the chamber, wherein the first nozzle is configured to direct cooling medium directly onto the metal body during deformation, and wherein the second nozzle is configured to direct cooling medium onto the deformation device during deformation. Thus, efficient cooling through direct cooling and indirect cooling of the metal body can be achieved. The temperature control means may also comprise three or more independently controllable nozzles, wherein a third nozzle is configured to direct cooling medium into the chamber, and not directly onto the metal body or the deformation device. If the device for generating twin lamellas in a metal body comprises more than one deformation device, such as two deformation devices, at least two nozzles may be provided per deformation device, wherein the deformation devices are configured as described above.

According to one embodiment, said metal body is an elongated body, and said device comprises means for continuous introduction of said metal body into the chamber. Such means for continuous introduction of said metal body into the chamber may include any kind of drawing equipment operating with a pulling effect on the metal body.

According to one embodiment, the means for continuous introduction of said metal body into the chamber is at least one drawing block positioned inside the chamber, wherein the first nozzle is configured to direct cooling medium directly onto the metal body being wound onto the drawing block, and wherein the second nozzle is configured to direct cooling medium onto an inner wall of the drawing block. Direct and indirect cooling, by heat transfer metal to metal of the metal body is thereby achieved during drawing. This is in the present disclosure also referred to as a direct metal to metal coolant system. The at least one drawing block may in this case form part of the deformation device, which may be in the form of e.g. a drawing machine.

According to one embodiment, said device comprises a channel through which said elongated metal body is continuously introduced into the chamber, and the chamber has an outlet through which cooling medium in a gaseous state is permitted to leave the chamber and be introduced into said channel for the purpose of pre-cooling said metal body before the latter is introduced into the chamber.

According to one embodiment, said chamber is a generally closed chamber, and the device comprises means for controlled evacuation of cooling medium in a gaseous state from said chamber. Said means for controlled evacuation may include a control valve or similar equipment. A closed chamber is referred to as a chamber having a limited space which space is large enough for housing the essential parts of a deformation device by means of which said metal body is deformed in said chamber, but the space is yet small enough for enabling efficient cooling of the metal body therein with a low consumption of cooling medium. According to one embodiment, the volume, V, of said chamber is below 5 m³, according to another embodiment, V is below 3 m³, and according to yet another embodiment, V is below 2 m³.

According to one embodiment, said cooling medium source is a liquid nitrogen source.

According to one embodiment, said metal body is a wire or tube and said deformation device comprises at least one die for reduction of the diameter of the wire or tube.

Further features and advantages of the present disclosure will appear from the following detailed description, presented with reference to the annexed drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter, by way of example, the method and the device of the present disclosure will be described more in detail with reference to the annexed drawing on which:

FIG. 1 is a schematic representation of a device according to the disclosure, and

FIG. 2 shows the device of FIG. 1 in a view from above,

FIG. 3 is a cross section of a part of the device, taken along III-III in FIG. 1,

FIG. 4 is an end view of a part of the device, according to Iv-Iv in FIG. 1,

FIG. 5 is a schematic representation of parts of a device according to the disclosure, and

FIG. 6 is a schematic representation of parts of a device according to the disclosure.

DETAILED DESCRIPTION

FIGS. 1 and 2 show a device according to the present disclosure for generating twin lamellas in a metal body 1, said device comprising a chamber 2, a chamber inlet 3 connected to a cooling medium source 4, a deformation device 5 for deforming said metal body 1, said deformation device 5 being positioned inside said chamber 2, wherein the deformation device 5 is positioned so that the metal body Twill be surrounded by said cooling medium in a gaseous state while being deformed by said deformation device 5.

The device according to the present disclosure as presented in FIGS. 1 and 2 includes further means 6 for controlling the temperature inside said chamber 2 by controlling the introduction of cooling medium into the chamber 2. Here, said means 6 for controlling the temperature inside the chamber 2 includes a control valve 6 positioned in a conduit 7 which connects the cooling medium source 4 with the chamber 2 through the chamber inlet 3 and by means of which control valve 6 the cooling medium flowing towards the chamber 2 is controlled. There may be temperature sensors (not shown) that sense the temperature inside the chamber 2 and on the basis of which the control valve 6 is controlled.

Said chamber 2 is a generally closed chamber, at least during operation thereof, with a volume V of about 1.5 m³, wherein the device comprises means 8 for controlled evacuation of cooling medium in a gaseous state from said chamber 2. Here, said means 8 for controlled evacuation of cooling medium includes a control valve 8. The device includes a chamber outlet 9 and a channel 10 leading from said chamber outlet 9. The control valve 8 is positioned in said conduit 10. It should be emphasized that the control valve 8 is optional. The flow of cooling medium through the chamber 2 and through the channel 10 could be controlled solely by means of one or more valves, such as the previously mentioned valve 6, for controlling the flow of cooling medium from the cooling medium source 4 to the chamber 2.

In the embodiment shown in FIGS. 1-4, the metal body 1 is an elongated body, and said device comprises means for continuous introduction of said metal body into the chamber 2. The elongated metal body 1 is a wire, the diameter of which is to be reduced by the deformation device 5. It should be noted that the metal body 1 could, alternatively, be a tube. The deformation device 5 comprises a drawing machine 5 provided inside the chamber 2. Here, the drawing machine 5 comprises a first drawing block 12 and a second drawing block 13, a first die 14 and a second die 15. The drawing blocks 12, 13 have a pulling effect on the elongated metal body 1 and thereby form said means for continuous introduction of the elongated metal body 1 into the chamber 2. The dies 14, 15 are used for reducing the diameter of the elongated metal body 1 as the latter is pulled through the respective die 14, 15. The drawing blocks 12, 13 and the respective dies 14, 15 are arranged in series, such that the first drawing block 12 pulls the elongated metal body 1 through the first die 14 and the second drawing block 13 pulls the elongated metal body 1 through the second die 15. It should, however, be noted that other possible arrangements of drawing blocks and dies are possible within the scope of protection claimed for the present disclosure. For example, there may be only one die provided, or no die at all. In the latter case, the wire diameter is reduced as the metal body (wire) 1 is drawn between two drawing blocks. It is thus to be understood that what has heretofore been stated for embodiments including double drawing blocks is also applicable for embodiments in which there is only one drawing block present or embodiments in which there are more than two drawing blocks present. The deformation process may not even be a diameter reduction process but any other possible deformation process, such as bending, by means of which twin lamellas is to be formed in a metal body as the metal body is subjected to said deformation at a sufficiently low temperature.

FIGS. 3 and 4 show a cross section and an end view respectively of a part of the device including one of said drawing blocks 12, 13. The respective drawing block 12, 13 is carried by a respective shaft 16, 17 that penetrates a rear wall 18 of the chamber 2 and is driven by a respective motor 19, 20 provided outside the chamber 2. Power transmission parts 21, 22, such as gear wheels (not shown in detail), which may need lubrication by means of a lubricant and through which power is transmitted from the respective motor 19, 20 to the associated shaft 16, 17 are provided outside the chamber 2. Subjection of such parts to the temperatures attained inside the chamber 2 during operation of the device is thereby avoided. The drawing blocks 12, 13 and the respective shafts 16, 17 that carry them are horizontally arranged. Suspension arrangements 31, 32 carrying the respective drawing block 12, 13 and their associated shafts 16, 17 and transmission parts 21, 22 are also provided outside the chamber 2. Said suspension arrangements 31, 32 comprise bearings enabling rotation of rotatable parts such as said shafts in relation to stationary parts of the device.

As can be further seen in FIGS. 3 and 4, a front wall 23 of the chamber 2 may be opened by means of a power device 24, here a mechanically operated screw device. As an alternative, the power device 24 could be a hydraulically driven arm. Thereby, access to the inside of the chamber 2 is enabled. The walls defining the chamber 2 are arranged as double walls with a heat insulating material (not shown in the drawing) positioned therebetween, for the purpose enabling maintenance of low temperature inside the chamber 2 and avoiding excessive use of cooling medium.

FIG. 5 illustrates an embodiment of the provision of cooling medium from the cooling medium source 4 to the chamber 2. The cooling medium consists of nitrogen stored in the cooling medium source 4 in liquid state. Downstream the control valve 6, which is the main control valve, the conduit 7 from the cooling medium source 4 to the chamber 2 is subdivided in a number of branches, here three branches 33, 34, 35. A first branch 33 leads to a first nozzle 36 or opening through which the cooling medium is introduced into the chamber 2 in the region of the first drawing block 12 and the first die 14. A second branch 34 leads to a second nozzle 37 or opening through which the cooling medium is introduced into the chamber 2 in the region of the second drawing block 13 and the second die 15. It should be understood that there could be other alternative provisions of conduit branches and nozzles as well as alternative positioning thereof. A third branch 35 leads to the first die 14 and the second die 15 for the purpose of providing cooling medium to the respective die 14, 15 for the cooling thereof during operation. In each branch 33, 34, 35, there is provided a control valve 38, 39, 40 for controlling the flow of cooling medium therein. In the conduit 7, downstream the main control valve 6 and upstream the respective branch 33, 34, 35, there is provided a purge valve 41.

FIG. 6 illustrates another embodiment of the provision of cooling medium to the chamber 2 via the first branch 33, previously described with reference to FIG. 5. Downstream of the control valve 38, three more control valves 42, 43, 44 are provided, and additionally two more nozzles 45, 46. The control valve 42 is used to control the flow of cooling medium to the first nozzle 36, providing general cooling of the chamber 2 by emitting cooling medium into the chamber 2 in front of the first drawing block 12. The control valve 43 is used to control the flow of cooling medium to the nozzle 45, which is configured to direct cooling medium onto the metal body 1 as it is being wound onto the first drawing block 12. The control valve 44 controls the flow of cooling medium to the nozzle 46, which is configured to direct cooling medium onto an inside of the drawing block 12, thus indirectly cooling the metal body 1 via the drawing block 12. Of course, a corresponding provision of cooling medium via several nozzles and control valves may be arranged to the second drawing block 13 via the second branch 34.

In addition to the parts of the device mentioned above, the embodiment of the device of the present disclosure shown in FIGS. 1-4 further comprises an uncoiling plate 25 on which a wire coil 26 is positioned and uncoiled through a rotation of the uncoiling plate 25. The elongated metal body 1, here being described by said wire, extends from said uncoiling plate 25 to rectifier device 27 for straightening of the wire. Before entering the chamber 2, the metal body (the wire) 1 extends into the same channel 10 as is used for evacuation of gaseous cooling medium from the chamber 2. In said channel 10, the metal body (the wire) 1 is pre-cooled before entering the chamber 2 through the previously mentioned chamber outlet 9. The metal body 1 extends through the respective die 14, 15 of the deformation device 5, thereby being pulled by the respective drawing block 12, 13. Downstream the chamber 2 with its deformation device 5, there is provided a heating device 28 aimed for heating the metal body 1 as the latter passes through said heating device 28. Downstream the heating device 28, there is provided a printer 29 registering the speed with which metal body 1 passes it. Downstream the printer 29, there is provided a bending coiler 30 which winds the metal body 1, i.e. the wire, into a coil.

Although not shown in the drawing, there may be provided a fan inside the chamber 2, by means of which gaseous cooling medium inside the chamber is set into motion. An improved cooling effect on the metal body 1 is thereby achieved as the convection is increased. 

1. A method of generating twin lamellas in a metal body, comprising the steps of: introducing said metal body into a chamber; filling said chamber with a cooling medium having a temperature arranged to enable generation of twin lamellas in the metal body upon deformation thereof; and deforming said metal body while the metal body is surrounded by said cooling medium, wherein the cooling medium surrounding said metal body upon deformation of the metal body is in a gaseous state.
 2. The method according to claim 1, wherein the temperature inside the chamber is controlled by controlled introduction of said cooling medium into the chamber in at least two different locations within the chamber, wherein the cooling medium in a first location is directed directly onto the metal body being deformed, and in a second location is directed onto a deformation device used to deform said metal body.
 3. The method according to claim 1, wherein the cooling medium has a temperature in the range of about −80° C. to about −195° C.
 4. The method according to claim 1, wherein said cooling medium consists essentially of nitrogen.
 5. The method according to claim 1, wherein said cooling medium is introduced in a liquid state into the chamber and is permitted to change to a gaseous state once introduced into said chamber.
 6. The method according to claim 1, wherein said metal body is an elongated body which is continuously introduced into said chamber through an opening in the chamber, and wherein the cooling medium in a gaseous state is taken from the chamber and used for pre-cooling of parts of said metal body that have yet not been introduced into the chamber.
 7. The method according to claim 1, wherein said metal body is a wire or tube and wherein said deformation of said metal body inside said chamber includes a reduction of a thickness of the-wire or tube.
 8. A device for generating twin lamellas in a metal body, said device comprising: a chamber; a chamber inlet connected to a cooling medium source; and a deformation device for deforming said metal body, said deformation device being positioned inside said chamber, wherein the deformation device is positioned so that the metal body will be surrounded by said cooling medium in a gaseous state while being deformed by said deformation device.
 9. The device according to claim 8, further comprising temperature control means for controlling the temperature inside said chamber by controlling the introduction of cooling medium into the chamber.
 10. The device according to claim 9, wherein said temperature control means includes at least a first and a second independently controllable nozzle positioned inside the chamber and each nozzle being configured to introduce cooling medium into the chamber, wherein the first nozzle is configured to direct cooling medium directly onto the metal body during deformation, and wherein the second nozzle is configured to direct cooling medium onto the deformation device during deformation.
 11. The device according to claim 10, wherein said metal body is an elongated body, and further comprising means for continuous introduction of said metal body into the chamber.
 12. The device according to claim 11, wherein the means for continuous introduction of said metal body into the chamber is at least one drawing block positioned inside the chamber, wherein the first nozzle is configured to direct cooling medium directly onto the metal body being wound onto the drawing block, and wherein the second nozzle is configured to direct cooling medium onto an inner wall of the drawing block.
 13. The device according to claim 11, further comprising a channel through which said elongated metal body is continuously introduced into the chamber, said chamber having an outlet through which cooling medium in a gaseous state is permitted to leave the chamber and be introduced into said channel for pre-cooling said metal body before the body is introduced into the chamber.
 14. The device according to claim 8, wherein said chamber is a generally closed chamber, and wherein the device further comprises means for controlled evacuation of cooling medium in a gaseous state from said chamber.
 15. The device according to claim 8, wherein said cooling medium source is a liquid nitrogen source.
 16. The device according to claim 8, wherein said metal body is a wire or tube and said deformation device includes at least one die for reduction of a diameter of the wire or tube. 